What mechanism causes clouds to move across the sky?
Where is this steering mechanism predominantly found?
In general, clouds move at a speed and direction of the prevailing wind at
the altitude where the clouds are occurring. The direction and speed of the
wind depends on the pressure differences between the areas of high and low
As you go up in altitue over a particular location, the winds will vary in
direction and speed. Usually, the speeds increase with altitude up to a
certain point, and then they decrease. Rivers of fast-moving air in the
atmosphere are called "jet streams," and occur at altitudes from 25 to 40
thousand feet above the ground. Speeds in the jet stream can reach as high
as 175 miles per hour or more. When clouds occur at that level, they move
very quickly. The location and strength of the jet stream has a big effect
on the weather at a particular location.
At a lower level, the the windspeed may be different, and the direction may
be different as well. Sometimes you can see clouds at several different
levels, and they may be moving in different directions.
Meteorologists track the movement of clouds continuously with satellites,
and with weather balloon measurements from selected locations twice a day.
This information helps the meteorologists forecast the weather.
Wendell Bechtold, Meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO
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Update: June 2012